This invention is generally relative to a wireless Ultra Wideband (UWB)-based space-time sensor networks communication.
In order to collect data of interest, sensor networks communications often scatter multiple sensor nodes over a limited geographic region. The collected data is then analyzed to expeditiously achieve or facilitate a given mission objective. It does not matter whether the collected data is continued surveillance, reconnaissance, target identification, registration and disposition, or anything else along those lines. Each of the sensor nodes in the sensor networks communications is expected to reliably and securely transmit its data to a receiver for further analysis, pattern recognition, coordination, and processing during various time intervals. Different sensor nodes in the sensor networks communications may be responsible for different levels of throughput and fidelity depending on a particular task. In some cases, some of sensor nodes in the sensor networks communications may have to provide several transmissions within a short-time interval while other sensor nodes may only transmit at irregular intervals or even not at all. Thus, resource allocations of the sensor networks communications need be determined and continually reassessed so that accommodations of such versatility can be achieved in performance.
In the next generation, further sensor networks communications are envisioned to contain a large number of sensor nodes. Each of the sensor nodes has a limited capability in terms of computation, communication and sensing capabilities, and operates in an unattended mode with limited energy. The sensor nodes in the further sensor networks communications are characterized by severe energy constraints because sensor nodes have to operate with finite battery resources. Generally speaking, the further sensor networks communications have several properties as follows: (1) Sensor networks communications is composed of a large number of sensor nodes that are densely deployed either inside the phenomenon or very close to it; (2) Sensor nodes are prone to failures; (3) A topology of the sensor networks communications changes very frequently with times; (4) Sensor nodes usually use a broadcast communication paradigm; (5) Sensor nodes have limited power, computational capacities, signal processing, transmit, and memory; and (6) in some cases, sensor nodes may not have global identification because the sensor networks communications use a larger amount of overhead and large number of sensor nodes.
The sensor networks communications has many applications either in commercial business or in military environments. One is used to monitor and control the safety critical military and governmental environmental such as domestic infrastructure systems. In this case, the application of the sensor networks communications may include battlefield detection and protection systems for biological, chemical and/or radiological weapons, aiding areas hit by disasters. Another application is used for homeland security at airports, bridges, public building, and major subway train systems. A third application is used for tracking. For example, a ship in the ocean emits sounds that may be detected and characterized by several underwater sensor networks. As the ship moves, the bearing measurements slowly change. A fourth application is in smart spaces that may include semiconductor and/or manufactory facilities, smart building, cities, and even sensitive laboratories. A fifth application is used to monitor ground temperature such as a forest to detect fast moving forest fires. A sixth application is in entertainment environment including amusement parks and/or museums. In addition, other applications are in health care systems such as higher-age health monitor and/or patient health and movement status in hospital or at home environment. Hence, the sensor networks communications has tremendous application value not only in military battlefield but also in commercialization.
Recent advances in integrated circuits technology have enabled mass production of tiny, cost-effective, and energy-efficient seamless sensor nodes with processing capabilities. A seamless sensor node is usually equipped with a sensor module which detects via electrical/electromagnetic fields, acoustics, optical, movement, chemicals, biological agents, radiation, environmental factors such as humidity, temperature, etc. Characteristics of seamless sensor nodes to be considered are size, battery consumption, energy level, lifetime, movement (whether the sensor is mobile or must remain stationary), position (whether the sensor node may be embedded or may be independent of its surroundings), redundancy for checking integrity, and failure modes. The malfunctions may indicate that the sensor node has failed, is degrading slowly, or possesses Byzantine behavior such as going up and down randomly.
Advanced sensor networks communications is expected to deploy a larger number of size sensor nodes, such as 1000, or even more individual sensor nodes in potentially hostile and militarily sensitive environments. Sensor nodes can be either thrown in as a mass or placed one-node by one-node in the sensor field. In particular, the sensor nodes can be deployed by using several methods: (1) dropping from an air plane, such as an unmanned plane; (2) delivering in an artillery shell, missile or rocket; and (3) placing a sensor node either by a human or a robot, etc. Furthermore, additional sensor nodes can be redeployed to replace malfunctioning nodes because of changes in task dynamics at any time.
Each of the sensor nodes in the sensor network communications is likely to support data collection and transmission in an efficient, robust, reliable, and secure communication fashion. However, the sensor network communications will encounter multipath propagation because the sensor network elements are not likely to be guaranteed a line-of-sight transmission path to the receiver, which is usually not promised to remain at a fixed position for any period of time. Thus, the received signal from the sensor nodes is much weaker than the transmitted signal due to mean propagation loss. In addition to mean path loss, the received signal exhibits fluctuations in signal level because of fading. Moreover, the sensor networks communications may likely be jam resistant in a hostile and militarily sensitive or a battlefield. In most situations, battery recharging for the sensor nodes is impossible. Therefore, to effectively operate under the abovementioned constraints, we invent the use of UWB technologies along with MIMO-based space-time processing architecture for the sensor networks communications.
U.S. Federal Communications Commission (FCC) released the revision of Part 15 of the Commission's rules regarding UWB transmission systems to permit the marketing and operation of new products incorporating UWB technology On Apr. 22, 2002. With appropriate technology, UWB-based sensor nodes can operate using spectrum occupied by existing radio service without causing interference, thereby permitting scare spectrum resources to be used more efficiently. UWB technology that uses baseband pulse has recently drawn interest for wireless sensor network communications. The UWB technology requires no radio carrier frequencies because of employing baseband transmission. Thus, the UWB technology is resilient to multipath and jam interference. In addition, low transmission power and simple transceiver circuitry make UWB an attractive technology for wireless sensor networks communications.
The present invention of the wireless UWB-based space-time sensor networks communications has not only full capability for sensing data, source data encryption, computing and transmission as well as strategies that overcome signal multipath propagation effects, but also has an architecture scheme for a tiny, low-power, low-cost communication transceiver, sensing, and computing processing units in the sensor node. Thus, there is a continuing need of the wireless UWB-based space-time sensor networks communications.